166 Milk and Its Products 
globules; second, the amount of solids not fat in 
the milk; third, the character of the solids not 
fat. The larger the fat globules the more readily 
they separate from the milk, since the larger the 
sphere the less the ratio between the surface and 
the mass, so that a large fat globule meets with pro- 
portionately less resistance because of the viscosity 
of the milk than a small one. The size of the fat 
globules is to a great extent a characteristic of the 
breed and individuality of the animal, but cows 
newly calved secrete larger fat globules than those 
in advanced periods. of lactation; consequently we 
find that the milk from new milch cows is more 
readily creamed than from those long in milk. 
The amount of solids not fat affects creaming by 
the gravity process because of the difference it effects 
in the specific gravity of the fat and milk serum. 
The solids not fat are all heavier than water, and 
in the milk are in a state of solution or semi-solu- 
tion; hence, an increase in the amount of solids not 
fat increases the specific gravity of the milk ‘serum 
in which they are dissolved, and makes the differ- 
ence between the specific gravity of the fat and 
milk serum greater and the separation of the fat 
easier. The proportion of solids not fat is in- 
fluenced by the period of lactation and, to a con- 
siderable extent, by the character of the food. Cows 
far advanced in lactation often givé milk extremely 
rich in solids not fat. Cows fed on dry food give 
milk containing less water than those fed on watery 
or succulent foods. In so far as these conditions 
